1. Field of the Invention
The invention relates to a voltage regulator circuit, and more particularly to a voltage regulator circuit for controlling operations of internal elements of the voltage regulator circuit according to a periodic control signal so as to reduce the quiescent current.
2. Description of the Related Art
A voltage regulator circuit is adopted to provide a stable output voltage. FIG. 1 shows a basic architecture of a conventional voltage regulator circuit. Referring to FIG. 1, the voltage regulator circuit 10 includes a reference voltage generator 11, an error amplifier 12, a switch unit (pass element) 13, resistors R1 and R2, and a capacitor C1. The reference voltage generator 11 generates a constant reference voltage Vref as a reference voltage of the error amplifier 12. Meanwhile, the output voltage Vout of the voltage regulator circuit 10 is converted into another feedback voltage Vfb by way of the voltage-dividing principle (Equation (1)). At this time, the error amplifier 12 receives the two voltages, and generates a computed voltage in order to control the switch unit (e.g., MOS, Bipolar, etc.). Therefore the voltage regulator can provide a desired current suitable for the load. After the computation of the overall loop, the voltage regulator circuit finally obtains a stable output voltage, which is calculated according to Equation (2).Vfb=Vout*[R2/(R1+R2)]  (1)Vout=Vref*[1+(R1/R2)]  (2)
However, this basic voltage regulator circuit 10 has DC quiescent currents including a quiescent current (Iref) of the reference voltage generator 11, a quiescent current (lop) of the error amplifier 12 and a quiescent current (Idrive) of the load. Thus, when the voltage regulator circuit 10 is kept at a no-loading state (Iload=0), the system enters a so-called standby mode, and the quiescent currents Iref and lop still exist at the input terminal (Vin) of the voltage regulator circuit 10. Therefore, if the system power is provided by a battery, the demands of reducing the quiescent current and lengthening the battery life cannot be achieved.